A hand-carried rifle has a sight that aids the user of the rifle in aiming the rifle at the target. In one approach, fixed (sometimes termed “iron”) sights are affixed to the upper side of the barrel of the rifle and are aligned to aid the user to point the barrel. The fixed sights operate in the visible wavelength range and at unity magnification.
A rifle may instead be provided with a telescopic sight that magnifies the visible-range image of the target using conventional lenses. The telescopic sight makes it easier to aim the rifle at a distant target because the target is larger when viewed through the telescopic sight. The telescopic sight normally has a reticle structure that permits the telescopic sight to be precisely adjusted to account for distance, windage, and ballistic effects.
The sight may instead function electro-optically, so that the image of the target is formed electronically on a viewing screen. An electro-optical sight allows the image to be electronically adjusted for improved visibility (e.g., contrast enhanced) or electronically enlarged, and also allows the image to be formed with wavelengths other than those in the visible range. For example, an infrared sight converts an image in the infrared range to an image in the visible range for viewing by the human eye. The infrared imaging improves visibility at night and in other viewing conditions where the target is not readily viewed in the visible-wavelength range.
In the work leading to the present approach, the inventor has observed that the available electro-optical sights have the drawback that their functionality is lost in the event of a loss of power or a failure of the electronic circuitry. The user of the rifle is left without a sight, except in the event that the electro-optical sight is entirely removed to leave only fixed, unity-magnification sights (if the rifle is provided with fixed sights). In a critical situation, the loss of the electro-optical sighting capability can effectively render the rifle useless. Additionally, in some circumstances the user may simply elect to employ a conventional telescopic sighting capability in the visible range rather than a sight using electro-optical imaging to obtain the most useful image of the target.
The inventor has thus recognized a need for a sighted device that gives the user a range of options as to the selected sighting approach, as well as a useful fail-safe backup mode of operation in the event of electronic failure. The present invention fulfills this need, and further provides related advantages.